// ========================================================================
// Copyright (c) 2011 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
// You may elect to redistribute this code under either of these licenses.
// ========================================================================

package org.eclipse.jetty.servlet.listener;

import java.lang.reflect.Field;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.eclipse.jetty.util.Loader;
import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;

/**
 * ELContextCleaner Clean up BeanELResolver when the context is going out of service: See http://java.net/jira/browse/GLASSFISH-1649 See https://bugs.eclipse.org/bugs/show_bug.cgi?id=353095
 */
@SuppressWarnings({ "unchecked", "rawtypes" })
public class ELContextCleaner implements ServletContextListener
{

	private static final Logger LOG = Log.getLogger(ELContextCleaner.class);

	public void contextInitialized(ServletContextEvent sce)
	{}

	public void contextDestroyed(ServletContextEvent sce)
	{
		try
		{
			//Check that the BeanELResolver class is on the classpath
			Class beanELResolver = Loader.loadClass(this.getClass(), "javax.el.BeanELResolver");

			//Get a reference via reflection to the properties field which is holding class references
			Field field = getField(beanELResolver);

			//Get rid of references
			purgeEntries(field);

			LOG.info("javax.el.BeanELResolver purged");
		}

		catch (ClassNotFoundException e)
		{
			//BeanELResolver not on classpath, ignore
		} catch (SecurityException e)
		{
			LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
		} catch (IllegalArgumentException e)
		{
			LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
		} catch (IllegalAccessException e)
		{
			LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
		} catch (NoSuchFieldException e)
		{
			LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
		}

	}

	protected Field getField(Class beanELResolver)
		throws SecurityException, NoSuchFieldException
	{
		if (beanELResolver == null)
			return null;

		return beanELResolver.getDeclaredField("properties");
	}

	protected void purgeEntries(Field properties)
		throws IllegalArgumentException, IllegalAccessException
	{
		if (properties == null)
			return;

		if (!properties.isAccessible())
			properties.setAccessible(true);

		ConcurrentHashMap map = (ConcurrentHashMap)properties.get(null);
		if (map == null)
			return;

		Iterator<Class> itor = map.keySet().iterator();
		while (itor.hasNext())
		{
			Class clazz = itor.next();
			LOG.info("Clazz: " + clazz + " loaded by " + clazz.getClassLoader());
			if (Thread.currentThread().getContextClassLoader().equals(clazz.getClassLoader()))
			{
				itor.remove();
				LOG.info("removed");
			}
			else
				LOG.info("not removed: " + "contextclassloader=" + Thread.currentThread().getContextClassLoader() + "clazz's classloader=" + clazz.getClassLoader());
		}
	}
}
